The overall objective of the proposed research program is to achieve a basic knowledge and understanding of the filariae of man through study of the parasites in the laboratory in primate hosts. Loa loa, Dipetalonema perstans and other perstans-like filariae, and Onchocerca volvulus have been selected for study. The morphology, development, maturation and behavior of Loa loa obtained from man will be studied in experimentally-infected patas monkeys, baboons and rhesus monkeys. An American deerfly, Chrysops atlanticus, will be used as a laboratory vector. Attempts will be made to ascertain the factors or circumstances which stimulate the migration of adult worms through the superficial tissues of the host and other pathological processes. Comparative study of the adult and microfilaria stages of D. perstans of man and its counterpart, D. vanhoofi in chimpanzees, will be carried out in an effort to resolve the question of whether the two represent a single species (D. perstans) shared by man and primates. Efforts will be made to establish the life cycle of the simian parasite in the laboratory and learn more about the biology of the parasite, its interactions with its host and attendant pathological changes. Surveys of primates will be conducted in an effort to determine which other filariae may be shared accidentally or otherwise by man and lower primates. Also, efforts will be made to develop a convenient laboratory model for Onchocerca volvulus of man through experimental transmission of the human parasite, maintained in chimpanzees, to other primates. Alternatively, attempts will be made to establish other animal species of Onchocerca in primate hosts as models for the study of the biology of the parasite.